1. Field of the Invention
This invention relates generally to postage meters and more particularly to providing a secure meter system wherein printing and accounting stations are interconnected through an insecure link.
2. Brief Description of the Prior Art
Security factors have been of paramount significance in the design and construction of postage metering systems. Postal authorities have required adequate security devices to insure that postage printed is accounted for. With prior mechanical and electromechanical postage metering devices, security has been achieved through the employment of a single secure housing containing both the printing device and accounting registers. The housing generally included means for the ready detection of any unauthorized attempts to alter the accounting registers and/or attempts at the printing of postage without the recording of same in the accounting registers.
In U.S. Pat. No. 3,978,457 issued Aug. 31, 1976 and assigned to the assignee of the present invention, a microcomputerized electronic postage meter system was disclosed. Implementation of this system will greatly enhance postage accounting capabilities and facilitate new meter designs, as well as fully automated mail handling systems, wherein articles to be mailed can be sealed, weighed and the postage automatically applied thereto.
In order to preserve a high level of system integrity, security requirements dictated constraints upon system design. For example, in large console mailing systems optimum design considerations might suggest the placement of postage accounting processing means remote from the postage printing means. The servicing of such systems was difficult and cumbersome because security seals inhibited the servicing of components which were otherwise accessible.
Furthermore, security considerations placed constraints upon utilizing removable accounting processors which could be carried to the postal authorities for resetting. Naturally, large automated mailing consoles could not be physically removed and brought to a post office for resetting the accounting means.
Among the security problems inherent with the employment of separable printing and accounting stations was the possibility that one could gain access to an insecure communications link between separable elements and generate signals which would permit the printing of postage without the accounting for same at the accounting station.